#include<stdio.h>

//https://www.nowcoder.com/practice/0b97367cd2184c12a0e02f7c223aee11?tpId=290&tags=&title=&difficulty=0&judgeStatus=0&rp=0&sourceUrl=%2Fexam%2Foj%2Fta%3FtpId%3D290

int main()
{
    int n = 0;
    int sum = 0;
    scanf("%d", &n);
    if (n % 2 == 0) {
        sum = -n / 2;
    } else {
        sum = n / 2 + 1;
    }
    printf("%d", sum);
    return 0;
}
